Electrochemical measurement cell

Abstract

An electrochemical cell comprising two electrodes, wherein one of said electrodes is suitable for use as a reference electrode in electrochemical measurements, said device comprising (a) a capillary fill cell capable of receiving a small volume of aqueous sample liquid, said cell incorporating (b) a redox electrode located within said capillary fill cell, and (c) a reagent layer comprising quinhydrone located in said cell in a dry adherent water-soluble layer adherent to an inner surface of said cell opposite to or overlying said redox electrode and capable of dissolving during use in aqueous sample liquid in the region of said redox electrode.

We claim: 
     
       1. An electrochemical device comprising two electrodes, wherein one of said electrodes is suitable for use as a reference electrode in electrochemical measurements, said device comprising (a), a capillary fill cell capable of receiving a small volume of aqueous sample liquid, said cell incorporating (b) a redox electrode which may be the reference electrode located within said capillary fill cell, and (c) a reagent layer comprising quinhydrone located in said cell in a dry adherent water-soluble layer adherent to an inner surface of said cell opposite to or overlying said redox electrode and capable of dissolving during use in aqueous sample liquid in the region of said redox electrode. 
     
     
       2. An electrochemical device according to claim 1, further comprising (d) a reagent layer comprising pH buffer material located in said cell in a dry adherent water-soluble layer adherent to an inner surface of said cell opposite to or overlying said redox electrode and capable of dissolving in aqueous liquid in the region of said redox electrode, thereby to render said redox electrode useful as a reference electrode 
     
     
       3. An electrochemical device according to claim 1, wherein one of said electrodes is a reference electrode and a further electrode constitutes said redox electrode (c) and has associated therewith said reagent layer (d) comprising quinhydrone, thereby to render said cell suitable for the measurement of pH in a small quantity of aqueous liquid sample. 
     
     
       4. An electrochemical device according to claim 3, comprising a cell suitable for the measurement of pH in a small quantity of aqueous liquid sample, said device comprising (a) a capillary-fill cell, said cell incorporating (b) two redox electrodes of similar construction to each other formed as laterally-spaced layers of electrode material each adherent to a wall of said cell, said cell also incorporating (c) a reagent layer comprising quinhydrone located in said cell in a dry adherent water-soluble layer adherent to an inner surface of said cell opposite to or overlying each of said redox electrodes and capable of dissolving in aqueous liquid in the region of said redox electrodes, and (d) a reagent layer comprising pH buffer material in dry form located in said cell in the region of one only of said two electrodes. 
     
     
       5. An electrochemical device according to claim 3, wherein said reference electrode is a halide-sensitive metal-metal-halide electrode, with which is associated a reagent layer comprising a standard quantity of soluble halide ion in the form of a dry adherent water-soluble layer adherent to an inner surface of said cell opposite to or overlying said metal-metal-halide electrode and capable of dissolving in aqueous liquid in the region of said metal-metal-halide electrode. 
     
     
       6. An electrochemical device according to claim 1, wherein said capillary fill cell has a width of up to about 150 microns. 
     
     
       7. An electrochemical device according to claim 1, wherein at least one of said electrodes comprises a screen-printed layer of conductive particles adherent to a wall of said capillary fill cell. 
     
     
       8. An electrochemical device according to claim 7, wherein said conductive particles comprise particles selected from graphite, silver, gold or platinum, optionally overlaid with carbon particles. 
     
     
       9. An electrochemical device according to claim 1 wherein said reagent layer comprises a screen-printed layer of reagent material together with a thickener either adherent to a wall of said capillary fill cell opposite to one said electrode or overlying one said electrode. 
     
     
       10. An electrochemical device according to claim 9, wherein said thickener comprises polyvinylpyrrolidone. 
     
     
       11. An electrochemical device according to claim 9, wherein a reagent layer comprising quinhydrone also comprises a pH buffer material or a water-soluble halide.